Chapter VIII

A NOTION is very prevalent that in the continuous progress of science some substitute for coal will be found—some source of motive power as much surpassing steam as steam surpasses animal labour.

The popular scientific writer Dr. Lardner, in the following passage of his Treatise on the Steam Engine, contributed to spread such notions—in him, as a scientific man, inexcusable.[1] "The enormous consumption of coals, produced by the application of the steam-engine, in the arts and manufactures, as well as railways and navigation, has, of late years, excited the fears of many as to the possibility of the exhaustion of our coal-mines. Such apprehensions are, however, groundless. If the present consumption of coal be estimated at sixteen millions of tons annually, it is demonstrable that the coal-fields of this country would not be exhausted for many centuries.

"But, in speculations like these, the probable, if not certain, progress of improvement and discovery ought not to be overlooked; and we may safely pronounce that, long before such a period of time shall have rolled away, other and more powerful mechanical agents will supersede the use of coal. Philosophy already directs her finger at sources of inexhaustible power in the phenomena of electricity and magnetism. The alternate decomposition and recomposition of water, by magnetism and electricity, has too close an analogy to the alternate processes of vaporization and condensation not to occur at once to every mind; the development of the gases from solid matter, by the operation of the chemical affinities, and their subsequent condensation into the liquid form, has already been essayed as a source of power. In a word, the general state of physical science at the present moment; the vigour, activity, and sagacity with which researches in it are prosecuted in every civilized country; the increasing consideration in which scientific men are held, and the personal honours and rewards which begin to be conferred upon them: all justify the expectation that we are on the eve of mechanical discoveries still greater than any which have yet appeared; and that the steam-engine itself, with the gigantic powers conferred upon it by the immortal Watt, will dwindle into insignificance, in comparison with the energies of nature which are still to be revealed; and that the day will come when that machine, which is now extending the blessings of civilization to the most remote skirts of the globe, will cease to have existence, except in the page of history."

Such high-sounding phrases would mislead no scientific man at the present day; but there is a large class of persons whose vague notions of the powers of nature lay them open to the adoption of paradoxical suggestions. The fallacious notions afloat on the subject of electricity especially are unconquerable. Electricity, in short, is to the present age what the perpetual motion was to an age not far removed. People are so astonished at the subtle manifestations of electric power, that they think the more miraculous effects they anticipate from it the more profound the appreciation of its nature they show. But then they generally take that one step too much which the contrivers of the perpetual motion took—they treat electricity not only as a marvellous mode of distributing power, they treat it as a source of self-creating power.

The great advances which have been achieved in the mechanical theory of nature, during the last twenty or thirty years, have greatly cleared up our notions of force. It has been rendered apparent that the universe, from a material point of view, is one great manifestation of a constant whole of force. The motion of falling bodies, the motions of magnetic or electric attractions, the unseen agitation of heat, the vibration of light, the molecular changes of chemical action, and even the mysterious life-motions of plants and animals, all are but the several modes of greater or lesser motion, and their cause one general living force.

These views lead us at once to look upon all machines and processes of manufacture as but the more or less efficient modes of transmuting and using force. If we have force in any one of its forms, as heat, light, chemical change, or mechanical motion, we can turn it, or may fairly hope to turn it, into any other of its forms. But to think of getting force except from some natural source, is as absurd as to think of making iron or gold out of vacant space.

We must look abroad then to compare the known sources of force. Some distinct sources are of inconsiderable importance, such as the fall of meteoric stones, the fall of rocks, or the heat derivable from sulphur, and other native combustible substances. The internal heat of the earth, again, presents an immense store of force, but being powerfully manifested only in the hot-spring or the volcano, it is not available to us.

The tides arising from the attractions of the sun, earth, and moon, present another source of power, which is, and often has been, used in one way or another, and shall be considered.

The remaining natural sources of force are the complicated light, heat, chemical and magnetic influences of the sun's rays. The light, or chemical action, is the origin of organic fuel, in all its forms of wood, peat, bitumen, coal, &c.; while the heat occasions the motions of the winds and falling waters. The electricity of the air and the thunder-storm, and the electric currents of the earth, are probably secondary effects of the other influences. Among these several manifestations of force, our choice must, in all reasonable probability, be made.

Now it will be easily seen that nature is to us almost unbounded, but that economy consists in discovering and picking out those almost infinitesimal portions which best serve our purpose. We disregard the abundant vegetation, and live upon the small grain of corn; we burn down the largest tree, that we may use its ashes; or we wash away ten thousand parts of rock, and sand, and gravel, that we may extract the particle of gold. Millions, too, live, and work, and die, in the accustomed grooves for the one Lee, or Savery, or Crompton, or Watt, who uses his minute personal contribution of labour to the best effect.

So material nature presents to us the aspect of one continuous waste of force and matter beyond our control. The power we employ in the greatest engine is but an infinitesimal portion withdrawn from the immeasurable expense of natural forces.[2] But civilization, as Liebig said, is the economy of power, and consists in withdrawing and using our small fraction of force in a happy mode and moment.

The rude forces of nature are too great for us, as well as too slight. It is often all we can do to escape injury from them, instead of making them obey us. And while the sun annually showers down upon us about a thousand times as much heat-power as is contained in all the coal we raise annually; yet that thousandth part, being under perfect control, is a sufficient basis of all our economy and progress.

The first great requisite of motive power is, that it shall be wholly at our command, to be exerted when and where and in what degree we desire. The wind, for instance, as a direct motive power, is wholly inapplicable to a system of machine labour, for during a calm season the whole business of the country would be thrown out of gear. Before the era of steam-engines; windmills were tried for draining mines; "but though they were powerful machines, they were very irregular, so that in a long tract of calm weather the mines were drowned, and all the workmen thrown idle. From this cause, the contingent expenses of these machines were very great; besides, they were only applicable in open and elevated situations."

No possible concentration of windmills, again, would supply the force required in large factories or iron works. An ordinary windmill has the power of about thirty-four men,[3] or at most, seven horses. Many ordinary factories would therefore require ten windmills to drive them; and the great Dowlais Ironworks, employing a total engine power of 7,308 horses,[4] would require no less than 1,000 large windmills!

In navigation the power of the wind is more applicable, as it is seldom wanting in the open sea, and in long voyages the chances are that the favourable will compensate the unfavourable winds. But in shorter voyages the uncertainty and delay of sailing vessels used to be intolerable. It is not more than forty years since passengers for Ireland or for the Continent had sometimes to wait for weeks until a contrary wind had blown itself out. Such uncertain delays dislocate business, and prevent it from proceeding in the rapid and machine-like manner which is necessary for economy. Hence the gradual substitution of steam for sailing vessels. In the steam boiler, indeed, we have the veritable bag of Æolus; and thus, though steam is a most costly power, it is certain, and our sea captains are beginning to look upon wind as a noxious disturbing influence. In a well-established and connected system of communications, there is little or no use, and often a good deal of harm, in reaching a place before the appointed time. Thus there is a tendency to decline the aid of sails even when the wind is favourable and strong, and, unless for the purpose of saving fuel, a point little attended to as yet, it cannot be said that there is any benefit to be derived from sails equivalent to their trouble and cost. It is certainty that is the highest benefit of steam communication.

The regularity and rapidity of a steam vessel render it an economical mode of conveyance even for a heavy freight like coal. The first cost of a steam collier is five times as much as for sailing colliers of equal tonnage. But then capital invested in the steam vessel is many times as efficient as in the sailing vessel. A steam collier can receive her cargo of 1,200 tons at Newcastle in four hours, reach London in thirty-two hours, discharge by steam hydraulic machinery in ten hours, and return to Newcastle with water ballast within seventy-six hours for the round voyage. A single collier has been known to make fifty-seven voyages to London in one year, delivering 62,842 tons of coal with a crew of twenty-one persons. To accomplish the same work with sailing colliers would require sixteen vessels, and 144 hands.[5]

The same necessity for regularity may be still more clearly seen in land conveyance. A wind-waggon would undoubtedly be the cheapest kind of conveyance if it would always go the right way. Simon Stevin invented such a carriage, which carried twenty-eight persons, and is said to have gone seven leagues an hour.[6] Sailing coal-waggons were tried by Sir Humphrey Mackworth at Neath about the end of the seventeenth century, and Waller eulogizes these "new sailing waggons, for the cheap carriage of his coal to the waterside, whereby one horse does the work of ten at all times; but when any wind is stirring (which is seldom wanting near the sea), one man and a small sail do the work of twenty."[7]

Nearly a century later Richard Lovell Edge-worth spent forty years' labour in trying to bring wind carriages into use. But no ingenuity could prevent them from being uncertain: and their rapidity with a strong breeze was such, that, as was said of Stevin's carriage, "they seemed to fly, rather than roll along the ground." Such rapidity not under full control must be in the highest degree dangerous.

"Nothing could at first sight have seemed more improbable than the success of the steam locomotive over the atmospheric locomotive. The power of the air, which was absolutely gratuitous, was proved to be capable of impelling railway carriages as effectually as the power of steam, generated by coals which were procured at a great cost, and were brought from a considerable distance. But the conditions under which the force of the atmosphere could be applied were so onerous that the invention ceased to present the character of an aid, and its use has consequently been discontinued."[8]

It is the characteristic of certainty which led Brindley strongly to prefer canals to improved river navigations. Rivers he regarded as only fit to feed canals, and as being themselves subject to floods and droughts, he characterised them "as out of the power of art to remedy."[9] Many of Brindley's finest engineering works on the Bridge-water Canal were directed to warding off the interference of river floods. Yet even his great canal was subject to be frozen up in winter and to be let dry for repairs in summer, and we could not tolerate the inconvenience and loss which a stoppage of traffic would now occasion in our large and nicely-jointed system of trade.

Uncertainty will for ever render aërial conveyance a commercial impossibility. A balloon or aërial machine does not enjoy like a ship the reaction of a second medium. It is subject to the full influence of the wind. Thus, even if an aërial machine could be propelled by some internal power from fifty to a hundred miles an hour, it could not make head against a gale. To say nothing of the facts that balloon travelling must be dangerous, that it is really dependent on the use of fuel, and cannot, as far as we can yet see, ever be rendered practicable or cheap, it is, beyond all this, subject to natural uncertainty necessarily precluding its general use.

Atmospheric or terrestrial electricity has, no doubt, suggested itself to some as a source of power. The thunder-cloud, the aurora borealis, and the earth-current of the telegraphic wire, are natural manifestations of electric power, which might possibly be utilized. But such secondary forces are altogether inconsiderable in amount, compared with the forces of heat and wind, from which they doubtless arise. In fact, they are scarcely sensible, except during thunder, auroral or magnetic storms, when they become destructive, and interrupt our telegraphic communications. We should no more think of waiting for a magnetic storm to move our engines, than Brindley would have thought of waiting for a mountain torrent to float his canal boats. The first essential of a motive force is constancy; natural electricity, on the contrary, possesses all the characteristics of uncertainty and extreme irregularity, which are most opposed to utility.

We meet, however, a constant and manageable source of force in water power. The water-wheel, or the turbine, possesses a natural tendency to uniformity of motion, even more perfect than that bestowed on the engine by Watt's "governor." Water power is, in this respect, the best motive power, and is sometimes used on this account, where a very delicate machine requires to be driven at a perfectly constant rate. When an abundant natural fall of water is at hand, nothing can be cheaper or better than water power. But everything depends upon local circumstances. The occasional mountain torrent is simply destructive. Many streams and rivers only contain sufficient water half the year round, and costly reservoirs alone could keep up the summer supply. In flat countries no engineering art could procure any considerable supply of natural water power, and in very few places do we find water power free from occasional failure by drought.

The necessity, again, of carrying the work to the power, not the power to the work, is a disadvantage in water power, and wholly prevents that concentration of works in one neighbourhood which is highly advantageous to the perfection of our mechanical system. Even the cost of conveying materials often overbalances the cheapness of water power. The splendid Katrine Water Mills recently constructed by Mr. Fairbairn are in the best natural circumstances, and give a nominal power of 100 horses at an annual cost of 1,260l. But Mr. Fairbairn calculates that an equivalent force from coals, at 7s. per ton, would only cost 1,400l., and the difference is probably more than balanced by the cost of conveying raw materials and products to and from the mill, with the possibility, too, of an occasional scarcity of water during drought.[10]

It is usually possible, with more or less labour, to procure water power artificially, to store it up, and convey and expend it where we like. Those who are acquainted with Sir W. Armstrong's beautiful apparatus for working cranes, dockgates, and performing other occasional services, will probably allow that the most perfect conceivable system of machine labour might be founded on hydraulic power. Imagine an indefinite number of windmills, tidal-mills, and water-mills employed to pump water into a few immense reservoirs near our factory towns. Water power might thence be distributed and sold, as water is now sold for domestic purposes. Not only all large machines, but every crane, every lathe, every tool might be worked by water from a supply pipe, and in our houses a multitude of domestic operations, such as ventilation, washing, the turning of the spit, might be facilitated by water power.

The first suggestion of a system of storing and distributing power seems to be due to Denis Papin, the French refugee engineer, the same who suggested the use of the steam-engine piston.[11] In the Transactions of the Royal Society for the year 1687[12] he described a method of prolonging the action of water-wheels by drawing and forcing air through tubes, which seems to involve the principle of the boring machines of the Mont Cenis tunnel, the new coal-cutting machine, and pneumatic and hydraulic apparatus generally. And it was Bramah, a second French engineer, domiciled here, who first showed in practice the wonderful capabilities of hydraulic power. And so controllable, safe, clean, and irresistible is hydrostatic pressure, either of air or water, that, now our mechanical skill in construction is sufficiently advanced, it must come more and more into use. We might almost anticipate from its wide adoption a perfect Utopian system of machine labour, in which human labour would be restricted to the simple direction of the hydraulic pressure.

But before indulging in imaginary approximations to perfection, it is well to inquire into the several conditions of possibility. To the capabilities of hydrostatic pressure there is perhaps physically speaking scarcely a limit, but commercially speaking our command of water power, or hydrostatic power, in whatever form, is nearly limited to our command of steam. It is steam that presents us with hydrostatic power in its most abundant and available form. Water power in uniform abundance is to be had, in this country at least, only through steam; and all experience points to the fact that, instead of water being a possible commercial substitute for steam, it is steam that from its first use has been a substitute for water power.

A brief consideration of the history of the steam-engine will put this fact in the clearest light. Though water power had been in use since the time of the Romans, a great want was clearly felt in the seventeenth century of some new power, antithetical to water power, so to speak, and capable of overcoming it, so that drowned mines might be pumped dry, and water might be raised to furnish artificial water power, where a natural supply was not to be had. The earliest explicit patent for a new engine was directed to the raising of water,[13] and the "Exact and True Definition" of the Marquis of Worcester's engine clearly expressed a similar purpose.

"There being indeed no place but either wanteth water, or is overburdened therewith...by this engine either defect is remediable." Hence the Marquis calls his invention a "stupendous water commanding engine," and truly regarded it as a new primum mobile which was to overcome the force of falling water.

His appreciation of the value of water power is shown by his remarkable motto:[14]—

"Whosoever is master of weight is master of force,

Whosoever is master of water is master of both."

"And consequently," said he, "to him all forcible actions and achievements are easy, which are in any wise beneficial to, or for, mankind."

Savery had no less correct and exalted notions of what his engine might accomplish by simply overcoming the gravity of water. It generated an universal motive power; for he said, "I have only this to urge, that water in its fall from any determinate height, has simply a force answerable to, and equal to the force that raises it;"[15] and he hints at "what may yet be brought to work by a steady stream and the rotation, or circular motion of a waterwheel," and "what use this engine may be put to in working of mills, especially where coals are cheap."

Now during the greater part of last century the steam-engine did perform the duty alluded to; it did pump up water and furnish artificial water power for turning mills and winding coals from mines. At the Coalbrookdale Iron Works it accomplished an inestimable service by enabling Darby to maintain and increase the blast of his new coal furnaces, an atmospheric engine being used to return the water from the lower to the higher mill-pond.[16]

Had not the introduction of the crank, flywheel, and governor by Watt, enabled us to communicate equable circular motion directly from a steam-engine to a machine, the water-wheel supplied with water by an engine would to this day be the source of motive power. As it is, of course steam power used directly is cheaper than steam power used indirectly. Water power is now only used where a natural fall is easily available. Such falls had in general become monopolised property from time immemorial, and naturally became the seats of factory labour, half a century or more ago. But it was the steam-engine which alone could allow the growth of our factory system, as seen in the fact that steam power employed in factories now exceeds water power six-fold. In 5,117 textile factories existing in the United Kingdom in 1856, the power employed consisted of,[17]—

Horse power.

Steam power...

137,711

Water power...

23,724

Total...

161,435

The water-wheel, moreover, has, by the continued exertions of our great engineers, from Smeaton down to Fairbairn been carried near its mathematical maximum of efficiency, whereas the engine yet gives us only a fraction of the power it may be made to give. The improvement of the engine has, in fact, caused it to be substituted successively in many mills before worked by water; and could its efficiency be again doubled, as is not impossible, hardly could the best water power in the country withstand the superior economy of steam.

The predominance of steam over water is seen in many other instances. It is a steam-engine that is used to supply water power for Sir W. Armstrong's apparatus, as at the Liverpool and Birkenhead Docks. A handsome and lofty building will be seen near the Birkenhead Great Float, containing a reservoir of artificial water power thus obtained. Again, it is only the engine that can supply water for the manufacturing and domestic uses of our great towns like Manchester and London. Our factories, printworks, sugar refineries, breweries, and other works, find it a matter of immense cost and difficulty to get a plentiful supply of water from wells and pumping engines, or from natural sources. And if we can hardly supply our boilers with water, how can we dream of ever using water, instead of steam, in the cylinder, and as the motive power?

The predominance of steam is further seen in its actual substitution for the windmill, or the tidal mill. Wind-cornmills still go on working until they are burnt down, or out of repair; they are then never rebuilt, but their work is transferred to steam-mills. Yet the grinding of corn is a work most suitable to the variable power of the wind. Again, if there is anything which could be cheaply done by wind, it is the raising of large masses of water where occasional irregularities are of no consequence, the rain and wind mostly coming together. Yet the windmills long employed to drain the Lincolnshire Fens, as practised in Holland, were at last superseded by powerful steam-engines, on the recommendation of Mr. Rennie.[18] Tidal mills are no novelty. One is mentioned in the first page and column of the Domesday Book as existing at Dover. A tidal pump was long moved by the current under Old London Bridge, and supplied the City with water. A tidal corn-mill, too, of very ingenious construction, subsequently existed at Woolwich.[19] Not long ago Sir Robert Kane, in his "Industrial Resources of Ireland,"[20] supposed tidal mills to be capable of supplying motive power to Ireland.

The application of the tides to machine labour is rendered difficult on account of their variation from day to day. To gain a constant head of water always available we must either construct elaborate and costly high and low tide basins, or else we must use the variable tidal wheel to pump up water into a great reservoir. The estuary of the Dee is one of the places best adapted to give a vast tidal power, and an anonymous but apparently able engineer has calculated what power might be utilised there.[21] He considers that the equivalent steam power might be had at a capital cost of £4,000,000, a sum wholly insufficient to provide the tidal works. Hence he concludes that the tidal scheme would be at least commercially impracticable, and he doubts whether it would be at all possible mechanically speaking to construct embankments and tidal basins on loose sands.

And whatever schemes of this sort be proposed we should remember that the tendency of tidal docks and reservoirs to silt up is an insuperable objection in cost. Engineers, from the time of Brindley, have constantly found that there is nothing more nearly beyond the remedy of art than the silting up of harbours, docks, and reservoirs. The great new Birkenhead Docks are threatened with this evil, and a tidal mill and reservoir constructed on the opposite side of the Mersey about half a century ago was soon abandoned for a similar reason.

It will, therefore, appear obvious that if we are to have a water power millennium of machine labour, which is physically possible, it must yet be using steam as the ultimate source of power.

To go on to other suggestions, we may notice the very prevalent opinion that the electro-magnetic engine will some day supersede the steam-engine. Such an engine, however, must be worked by an electro-positive metallic element as the source of power. Now it is coal or fuel only by which we can smelt ores and obtain the metal required for the engine, and it is demonstrable that we should get far more force by using coal directly under a steam-engine boiler, than by using it to smelt metals for an electro-magnetic engine. After the exposure of the claims of such an engine by Baron Liebig,[22] I need not dwell upon it. The predominance of steam, too, is shown most clearly in the fact that the steam-engine is used conversely to turn Faraday's magneto-electric machines, and supply electricity for telegraph purposes, and for illuminating lighthouses. And while force is found to be the cheapest source of electricity, it is impossible that electricity should be the cheapest source of force. The electro-magnetic engine might be found a convenient device for applying or concentrating force in some particular circumstances, but the force must ultimately be furnished by coal.

Hitherto we have considered mechanical force only, but it is obvious that if coal were used up we should want some source of heat as well as force. A favourite notion is to employ wind, water, or tidal mills to turn magneto-electric machines, and by the stream of electricity produced to decompose water, thus furnishing a continuous supply of artificial gaseous fuel. Such a plan was proposed in the Times during the discussion on the French Treaty. But an answer, attributed to Dr. Percy of the School of Mines, soon appeared, showing the amount of fuel derivable to be inconsiderable. The waste of power must be vastly greater in such a process of transmutation than in the system of artificial water power which we have considered. Besides, if uniform experience is to be trusted, a steam-engine would be a much more economical means of turning the magneto-electric machines than either a wind, water, or tidal machine. We should therefore only use coal in a roundabout manner to generate a less valuable fuel. For the hydrogen gas generated, though in some instances valuable, would in general be immensely less convenient than coal. For equal weights, it gives about four times as much heat as coal, but hydrogen is so light that for equal volumes it gives one five-thousandth part as much heat. To compress it in a small space would require more force than the combustion of the fuel itself would furnish, and gas companies do not find it convenient to compress their gas. Hydrogen too has so much higher a diffusive power than coal-gas, that it could hardly be retained in gasometers or ordinary pipes. Even the loss of coal-gas by leakage is said to be nearly twenty-five per cent.

Of course it is useless to think of substituting any other kind of fuel for coal. We cannot revert to timber fuel, for "nearly the entire surface of our island would be required to grow timber sufficient for the consumption of the iron manufacture alone."[23] And I have independently calculated, from the known produce of continental forests,[24] and the comparative heat-producing values of timber and coal,[25] that forests of an extent two and a half times exceeding the whole area of the United Kingdom would be required to furnish even a theoretical equivalent to our annual coal produce. Practically, however, there are inconveniences about the use of timber that would altogether prevent it from nourishing a large manufacturing system. Wood fuel is superior to coal in the single case of the iron smelting furnace; but in most other uses, the greater bulk of wood, and the large areas of forest land over which it is spread, necessarily render it a costly and inefficient fuel compared with coal.

Peat, or turf, again, may no doubt be turned into fuel; but, in spite of what has been said in its favour by Sir R. Kane,[26] all experience shows that it is immensely inferior as regards cost and efficiency to coal. It is usually full, too, of phosphorus and sulphur, and thus has not even those advantages of purity which render timber so valuable for the iron blast furnace.

Petroleum has of late years become the matter of a most extensive trade, and has even been proposed by American inventors for use in marine steam-engine boilers. It is undoubtedly superior to coal for many purposes, and is capable of replacing it. But then, What is Petroleum but the Essence of Coal, distilled from it by terrestrial or artificial heat? Its natural supply is far more limited and uncertain than that of coal, its price is about 15l. per ton already, and an artificial supply can only be had by the distillation of some kind of coal at considerable cost. To extend the use of petroleum, then, is only a new way of pushing the consumption of coal. It is more likely to be an aggravation of the drain than a remedy.

Coal has all those characteristics which entitle it to be considered the best natural source of motive power. It is like a spring, wound up during geological ages for us to let down. Just as in alluvial deposits of gold-dust we enjoy the labour of the natural forces which for ages were breaking down the quartz veins and washing out the gold ready for us, so in our seams we have peculiar stores of force collected from the sunbeams for us. Coal contains light and heat bottled up in the earth, as Stephenson said, for tens of thousands of years, and now again brought forth and made to work for human purposes.

The amount of power contained in coal is almost incredible. In burning a single pound of coal there is force developed equivalent to that of 11,422,000 pounds weight falling one foot, and the actual useful force got from each pound of coal in a good steam-engine is that of 1,000,000 lbs. falling through a foot; that is to say, there is spring enough in coal to raise a million times its own weight a foot high. Or again, suppose a farmer to despatch a horse and cart to bring a ton of coals to work a portable engine, occupying four hours on the way. The power brought in the coal is 2,800 times the power expended in bringing it, and the amount of useful force actually got from it will probably exceed by 100 times or more that of the horse as employed in the cart. In coal we pre-eminently have, as the partner of Watt said, "what all the world wants—POWER." All things considered, it is not reasonable to suppose or expect that the power of coal will ever be superseded by anything better. It is the naturally best source of power, as air and water and gold and iron are, each for its own purposes, the most useful of substances, and such as will never be superseded.

Of course I do not deny that if our coal were gone, or nearly so, and of high price, we might find wind, water, or tidal mills, a profitable substitute for coal. But this would only be on the principle that half a loaf is better than no bread. It would not enable us to keep up our old efficiency, nor to compete with nations enjoying yet undiminished stores of fuel. And there is little doubt, too, that a century hence the steam-engine will be two or three-fold as efficient as at present, turning the balance of economy so far the more in favour of those who then possess coal, and against those who have to resort to water or wind.

This is a point which I must insist upon as finally decisive of the question. The progress of science, and the improvement in the arts, will tend to increase the supremacy of steam and coal. Any mechanist knows that the water-wheel and the windmill have been brought, by the exertion of our engineers, Brindley, Smeaton, Rennie, Telford, and Fairbairn, near to their mathematical limit of efficiency; so that we can do little more than improve the mechanical construction, and gain some small percentage of additional power by reducing the friction of the machinery. The steam-engine, on the other hand, at least equally admits of improvement in mechanical details; but beyond this, in the principles of heat and vapour, we see clearly the possibility of multiplying at least three-fold the efficiency of fuel. If there is anything certain in the progress of the arts and sciences it is that this gain of power will be achieved, and that all competition with the power of coal will then be out of the question. In short, the general course of science and improvement will only lead us the more to regret the limited extent of our coal resources.

But let us further remember that coal is now a pre-eminent gift in our actual possession, whereas if any wholly new source of power be some day discovered, we have no reason to suppose that our island will be as pre-eminently endowed with it as with coal.

Mr. Babbage has applied his rare genius to this question, and what he has once said is incapable of improvement. Passing over the period which this work considers, when coal will be scarce here and plentiful elsewhere, he has thrown his thoughts forward to the time when coal will be scarce everywhere. Heat, he thinks, may then be got from the hot springs of Ischia. "In Iceland," he continues,[27] "the sources of heat are still more plentiful; and their proximity to large masses of ice seems almost to point out the future destiny of that island.... In a future age power may become the staple commodity of the Icelanders."

Power is at present our staple commodity, and Mr. Babbage clearly saw, more than thirty years ago, that with our coal power must pass from us.

Among the residual possibilities of unforeseen events, it is just possible that some day the sunbeams may be collected, or that some source of force now unknown may be detected. But such a discovery would simply destroy our peculiar industrial supremacy. The study of electricity has already been zealously cultivated on the Continent with this view,—"England," it is said, "is to lose her superiority as a manufacturing country, inasmuch as her vast store of coals will no longer avail her, as an economical source of motive power."[28] And while foreigners clearly see that the peculiar material energy of England depends on coal, we must not dwell in such a fool's paradise as to imagine we can do without coal what we do with it.

^Plutology; or, the Theory of Efforts to satisfy Human Wants. By W. E. Hearn, LL.D. Professor of Political Economy in the University of Melbourne, 1864, p. 199. This work appears to me both in soundness and originality the most advanced treatise on political economy which has appeared, and it should be familiar to every student of the science.